1. Field of the Invention
The present invention relates to a sheet feeder and an image forming apparatus, and more particularly to an air blowing type sheet feeder and an image forming apparatus having such sheet feeder.
2. Description of the Related Art
An image forming apparatus, such as copying machine, a printer, a facsimile machine, a printing machine, a composite machine or the like, is provided with a sheet feeder adapted to feed sheets stacked in a sheet storage section one by one. Examples of the sheet feeder include an air blowing type sheet feeder. The air blowing type sheet feeder has a configuration in which air is blown to the upper portion of an end face of a sheet bundle to thereby float sheets, and the floated sheets are conveyed while being separated one by one.
In the air blowing type sheet feeder, it is necessary to adjust air blowing amount so as to prevent the case where air blowing amount is too large and therefore the sheets might be conveyed in a state where two or more sheets ore superimposed on each other or the case where air blowing amount is too small and therefore no sheet is floated. Conventionally, the adjustment of the air blowing amount is previously performed by the distributor of the image forming apparatus for each different size and type of sheet.
However, due to different warpage of the sheet (which varies depending on temperature), different cutting condition of the sheet (which differs for each paper maker), and/or the like, appropriate air blowing amount may be different even for the sheets of the same size and type. Thus, before actually performing image forming process, the user has to float the sheets of the sheet feeder and operate an operation unit of the sheet feeder to fine-adjust the air blowing amount while confirming the floating state of the sheets by visual observation.
Further, there is also a proposal in which a camera is used to take an image between the uppermost sheet and the sheet below the uppermost sheet in a state where the sheets are floated, the distance between the two sheets is calculated based on the image taken by the camera, and the air blowing amount is automatically adjusted according to the calculated distance (see, for example, Japanese Unexamined Patent Application Publication No. 2010-254462).